What needs to be listed with all these "free food" coupons is they obviously get scanned from an original coupon printed in offset process. If you can trick a local merchant into taking them, fine more power to you, but these are obviously not valid originals.
There's no sense changing a .jpg (bitmap) into an .pdf (vector), that won't improve the quality one bit. An image needs to be created in .pdf format from the start in order to be scalable. If you want to print this out, just print it out as is, it being converted to pdf won't do a thing for it.